The determination of the distance between an observer and a target can, in particular in the case of weapon systems, be carried out by means of laser distance measuring devices. Laser distance measuring devices are based on the principle of measuring the transition time of an optical pulse from the observer to the target and back from the target to the observer. From the transition time of the optical pulse and the knowledge of the speed, the distance can be determined. The optical pulse or impulse is produced by a laser. Both diode lasers with low pulse power or pulse energy as well as a giant pulse laser with relatively high pulse power and pulse energy are used as a laser transmitter. In order to be able to achieve a sufficiently long range with the diode laser distance measuring devices, as a rule the lasers used are operated with a high pulse repetition rate and the backscattered energy of many laser pulses is added (so-called sampling principle). With giant pulse lasers, exactly one laser pulse is emitted and the backscattered radiation is detected with a receiver.
Giant pulse lasers are used in laser distance measuring devices to achieve long ranges of several kilometers. Depending on the transmission of the atmosphere and the particular reflective properties of the target, under favorable conditions ranges of more than 20 kilometers in distance can be achieved. However, if the laser beam of a giant pulse laser is incident on a highly reflective target at a short distance, the reflected pulse energy is so great that damage to the receiving diode or the receiver electronics can occur.
The invention disclosed in DE 102 15 109 B4 is based on the problem of designing a laser distance measuring device for a weapon system so that the receiver diode is not damaged by its own reflected radiation after aiming at a retroreflector. To solve said problem, a laser distance measuring device for a weapon system comprising a receiver diode, a device for switching on and off and a protective filter is proposed, in which the protective filter is switched on when a first reflected laser pulse is received, the device for switching on and off compares the energy of a reflected first laser pulse with a limit value and a second laser pulse is transmitted for distance measurement if the limit value is exceeded. However, considerable restrictions with the lasers that can be used arise through the protective filter that is used.
Based on this, it is the object of the present invention to provide a laser distance measuring device and a method for operating a laser distance measuring device of the aforementioned type that avoids the disadvantages of the prior art, in particular to ensure protection of the receiver against its own reflected radiation without limitations on the laser light source.
This object is achieved according to the invention by a laser distance measuring device and method with the features mentioned in the claims.